1. Field of the Invention
The present invention relates to a motion detecting apparatus for use in a closed circuit television, and more particularly to a motion detecting apparatus which is capable of editing a region of which the motion is to be monitored and adjusting a motion indication and an indication level.
2. Description of the Prior Art
Generally, in the closed circuit television (CCTV) a motion is detected by comparing a video signal obtained by a monitor camera with a mean valve and the detected motion is displayed on a screen. One conventional motion detecting apparatus for use in a CCTV is illustrated in FIG. 1. As shown in FIG. 1, the conventional motion detecting apparatus comprises a first and a second analog/digital converters 1a and 1b for converting an inputted video signal and a video signal delayed by one frame into a digital video signal, respectively, a frame or field comparator 3 for comparing the digital video signal of current frame and the one frame-delayed digital video signal both being outputted from the analog/digital converters 1a and 1b by frame or field and detecting the difference signal therebetween, a synchronous separator 2 for separating and detecting a synchronous signal of the input video signal, a window and marker indicator 5 for controlling a window indicating a motion detection region of which the size and position are determined by variable resistors VR2 and VR3 and a marker indication of a motion point in response to the synchronous signal of the synchronous separator 2, a memory and address controller 4 for generating a memory control and address control signal for detecting a motion and controlling the frame or field comparator 3 in response to the synchronous signal of the synchronous separator 2, a digital/analog converter 6 for converting the difference signal of the frame or field comparator 3 into an analog signal, a level comparator 7 for comparing the output signal from the digital/analog converter 6 with a reference level which is set by a variable resistor VR1 and outputting a motion signal, an alarm output controller 8 for outputting an alarm signal to a speaker (not shown) in response to the motion signal of the level comparator 7, a superimposer 9 for outputting a video signal, and a system clock signal generator 9a for generating a system clock signal which is required by the superimposer 9, the memory and address controller 4 and the window and marker indication controller 5.
In such a conventional motion detecting apparatus, a video signal from a monitor camera (not shown) is inputted to the first and second analog/digital converters 1a and 1b, the synchronous separator 2 and the superimposer 9. The first and second analog/digital converters 1a and 1b convert the currently inputted video signal and a video signal which has been inputted to a previous frame and is delayed by one frame into digital video signals to the frame or field memory 3. And the synchronous separator 2 separates a synchronous signal from the input video signal and applies the synchronous signal to the memory and address controller 4 and the window and marker indicator 5.
At this moment, the window and marker indicator 5 may vary the size of the window, which is a motion monitoring region, by the variable resistors VR2 and VR3. Also, the size of the marker may be varied by the window and marker indicator 5. At this moment, the shape of the window is set to a rectangular or a square type.
Thereafter, the frame or field comparator 3 compares the video signal of previous frame with the video signal of current frame at every frame and outputs a difference signal therebetween upon the control of the memory and address controller 4. And then, the difference signal between the current frame video signal and the previous frame video signal is converted into an analog signal by the digital/analog converter 6. That is, the difference signal is converted into a direct current level signal through an integral circuit. The output signal from the digital/analog converter 6 is compared with a reference level, which is set by the variable resistor VR1, at the level comparator 7 so that a motion detection signal is outputted. The motion detection signal is applied to the alarm output controller 8 to drive the speaker, thereby making an alarm in response to the motion detection.
However, the convertional motion detecting apparatus has disadvantages in that since the motion detection level or the window region are adjusted by a volume control, it is impossible to freely adjust and vary the size and position of window which indicates the region to be monitored, and the marker which indicates the motion is limited in its position and size, and a detection error may occur due to a temperature drift.
There has also been disadvantage in that since the motion is detected by comparing the input video signal with the mean value, a detection error may occur in the video signal of rapid motion.